1. Field of the Invention
The invention relates to a bumper arrangement for the front or rear of a car body of a motor vehicle that is shrouded by a skin panel.
2. Description of the Related Art
Different types of bumpers and bumper arrangements are known. For example, in German patent document 44 13 641 C1 a bumper is disclosed which has a transverse support designed as an energy absorbing member to be attached to the car body. At the front side of the transverse support impact members are arranged which are supported on the transverse support and are comprised of an energy-absorbing material which is preferably a plastic foam or a honeycomb structure of plastic material.
U.S. Pat. No. 5,154,462 discloses a bumper having a transverse support comprised of a C-shaped rear member, made of a first material, for example, steel, and fixedly connected to the longitudinal supports, and a C-shaped closure member covering the rear member and comprised of a second lighter material, for example, aluminum or fiberglass. Both members are joined such that they form a box-shaped hollow profiled member which is filled with an energy-absorbing material such as polypropylene or urethane foam.
In the German patent document 29 41 879 A1 a bumper configuration for a motor vehicle is disclosed which has a transverse support with a plurality of cutouts which are provided along its length at the front side of the transverse support. The cutouts are provided for receiving impact absorption members of urethane foam or polyethylene honeycombs.
In addition to the partially complicated and manufacturing-technologically complex configuration, all of the aforementioned embodiments have the disadvantage that they propose energy-absorbing members of plastic material, usually foamed foam bodies. Already the manufacture of these foam bodies may cause the release of environmentally hazardous materials. In particular, however, these members are disadvantageous in regard to recycling of motor vehicles. The employed plastic materials are often recyclable only with difficulties. Moreover, a separation of the metallic materials and the plastic materials is required for a proper recycling.
The German patent document 196 43 049 A1 discloses a bumper arrangement for the front or rear area of the car body of a motor vehicle. The bumper arrangement comprises a transverse support which is mounted by means of crash boxes on the longitudinal supports of the car body as well as a transverse beam which is provided under the transverse support and also supported on the longitudinal supports of the car body. However, this configuration is comparatively heavy and inflexible.
It is an object of the present invention to provide a bumper arrangement which in its basic concept avoids impact absorption members of plastic material and is improved with regard to its function, in particular, relating to the protection of pedestrians.
In accordance with the present invention, this is achieved in that the legs of the shell member comprise a grate structure of a plurality of adjacently arranged openings with ribs delimiting them.
Accordingly, the transverse support is comprised of a metallic shell member of a U-shaped cross-section with a stay and two legs, and the legs have a grate structure comprised of a plurality of adjacently arranged openings with ribs delimiting them.
Such a shell member is lightweight which is positive in the sense of weight reduction. However, its flexibility should be particularly stressed. During a crash at low force level at low speed, the transverse support will yield elastically. Upon surpassing a predetermined force level, the transverse support will deform plastically so that the energy resulting from the impact is converted into deformation work.
The inherent defined flexibility behavior of the transverse support contributes to achieving a greatest possible protection of pedestrians.
Expediently, the ribs extend in the longitudinal direction of the motor vehicle.
The flexibility behavior of the bumper arrangement can be realized in that the ribs are formed as rated buckling points. This can be achieved by a slightly angled or bent or buckled or curved extension of the ribs. Of course, the integration into the ribs of differently configured rated buckling points, which will yield flexibly in a defined manner upon surpassing a certain force level, is also conceivable.
In another advantageous embodiment, flanges adjoin the end of the legs of the shell member. These flanges contribute to a stiffening of the transverse support in the rearward area facing the longitudinal supports.
An especially advantageous further embodiment of the basic inventive principle is a bumper arrangement wherein the shell member is supported on an inner profiled member which is also transversely arranged relative to the longitudinal supports. The profiled member has preferably a U-shaped cross-section with laterally extending flanges adjoining its legs.
The flanges of the shell member can be supported on the flanges of the profiled member. Possible is, for example, a welded, riveted, screwed or adhesive connection of the shell member and the profiled member.
According to another preferred embodiment, the legs of the shell member and the legs of the profiled member extend from their respective stays, which are positioned at a spacing to one another, in a direction toward the longitudinal supports.
As a result of the stays of the shell member and the profiled member being spaced from one another, the transverse support has two planes with different force levels. In the case of an impact, first the outwardly positioned shell member is loaded and used for impact absorption and is elastically and/or plastically deformed in this connection. Once this absorption capacity has been used up or exhausted, the shell member and the profiled member jointly provide a resistance for an impact at a higher force level.
The energy absorption capacity of a bumper arrangement according to the invention can be further increased when the transverse support is connected by crash boxes and mounting plates to the longitudinal supports. The crash boxes are designed, in particular, to absorb energy resulting from an impact at higher force level by transforming the energy into deformation work. This can further reduce damage to parts of the supporting vehicle structure.
According to a further advantageous embodiment of the basic inventive principle, a transverse beam is provided under the transverse support.
By means of the transverse beam arranged under the transverse support, it is possible to provide for a front or rear crash an additional energy absorption in the area near the ground. In addition to the energy absorption, a further positive effect of this arrangement is that an obstacle is impacted with a larger surface area. This results in a change or alleviation of the impact. Moreover, the energy absorption is divided onto a further force level. This is advantageous, in particular, with respect to the protection of pedestrians.
Expediently, the transverse beam is supported by spacer stays (crash stays) and mounting plates on the longitudinal supports of the motor vehicle.
In certain applications, it is conceivable in the context of the invention to provide impact-absorbing damping members between the inwardly positioned profiled member and the outer shell member. Even though with the bumper arrangement according to the invention the elimination of plastic foam bodies is desired, this feature is not to be completely excluded. Such a bumper arrangement realizes a weight reduction and can provide an additional impact absorption capacity for use in connection with heavy motor vehicles.